The present invention relates generally to a system and a method for adjusting engine torque by controlling valve actuation.
In U.S. Pat. No. 6,009,841, an engine with a hybrid valvetrain is disclosed in which one intake valve is actuated by a source other than a camshaft. This first intake valve is randomly operable meaning that the valve opening and closing events are independent of engine crankshaft position, thus, a fully variable valve. A second intake valve is actuated by a camshaft and includes a deactivator. Operation of the second valve may be discontinued or restored within one engine cycle, termed selectable intake valve herein. The exhaust valve(s) of the hybrid valvetrain is conventionally camshaft actuated.
U.S. Pat. No. 5,647,312 teaches that air is admitted into the engine by a randomly operable intake valve when the engine is operating at a lower engine torque and lower engine speed; and engine torque is controlled by adjusting the opening lift height of the valve or the valve timing. U.S. Pat. No. 5,647,312 also teaches that air is admitted into the engine by a selectable intake valve when the engine is operating at a higher engine torque or engine speed; and, engine torque is controlled by adjusting the position of a throttle valve in the intake line. U.S. Pat. No. 5,647,312 fails to teach a method of controlling engine torque when both types of valves are operated. U.S. Pat. No. 6,009,841 does not disclose a method to control torque for any of the operating modes of the valves. The inventors have recognized a need to control torque throughout the entire engine operating range.
An internal combustion engine system having first and second intake valves and throttle valve in an intake line of the engine is provided with an engine controller to adjust a parameter related to engine torque of the engine primarily via the valve timing of the first intake valve when the first and second intake valves are activated. The first intake valve is a randomly operable intake valve with the valve timing being a closing time.
A method for controlling a parameter related to engine torque in an internal combustion engine is provided in which the engine comprises first and second intake valves, a throttle valve, and an engine controller. The method comprises the step of adjusting the parameter related to engine torque of the engine primarily via the valve timing of the first intake valve when the first and second intake valves are activated.
An advantage of the present invention is in providing smooth torque control throughout all operating regions of the engine. Adjusting closing time of the randomly operable intake valve is provided as a smooth torque altering method.
Other advantages, as well as objects and features of the present invention, will become apparent to the reader of this specification.